Field of the Invention
The present invention relates to an organic light-emitting display (OLED) device. More specifically, the present invention relates to an OLED device including an anti-oxidation layer for suppressing an organic light-emitting element from being damaged by oxygen (O2) plasma generated during a process of forming a transparent encapsulation layer to protect the organic light-emitting element.
Discussion of the Related Art
As the era of information technology has truly begun, the field of display devices has been rapidly growing, representing information in electrical signals in the form of visual images. In accordance with this, research is ongoing into various display devices, which need to be made thinner, lighter and more efficient in terms of power consumption. Display devices include a liquid crystal display (LCD) device, a plasma display panel (PDP) device, a field emission display (FED) device, an electro-wetting display (EWD) device, and an organic light emitting display (OLED) device, etc.
An OLED device is cable of producing light on its own (self-emissive). Thus, the OLED devices does not require an additional light source, unlike a liquid crystal display (LCD) device. Therefore, an OLED device can be made lighter and thinner than an LCD device. Further, an OLED device has advantages in that it is driven with low voltage to consume less power, and can present vivid colors, has fast response time, wide viewing angle and infinite contrast ratio (CR). For these reasons, an OLED device is currently considered as the next generation display device.
For a top-emission OLED device, a transparent electrode or a transflective (or a translucent or a semi-transparent) electrode is employed as a cathode in order to pass light generated (or emitted) in the organic light-emitting layer upwardly (i.e. towards the top) through the cathode. In addition, in order to ensure reliability of an OLED device, an encapsulation unit is formed on the organic light-emitting element including an organic light-emitting layer. Such layer is for protecting the organic light-emitting element from oxygen, moisture or physical impact or foreign matters (e.g., particles, debris or dust) possibly created during manufacturing process. In a top emission type OLED device, a glass encapsulation substrate or a thin-film encapsulation structure (encapsulation unit) in which an inorganic encapsulation layer and an organic layer are alternately stacked on one another for suppressing moisture permeation, etc. may be used as the encapsulation unit.
Such a thin-film encapsulation structure can reduce the thickness of flexible OLED devices, and thus much research is being conducted to improve thin-film encapsulation structures. Unfortunately, as an encapsulation unit is formed after an organic light-emitting element is formed, certain process constraints exist. For example, an encapsulation unit cannot be formed by a process carried out at a high temperature since the organic light-emitting layer would then be subject to undesirably high heat.
In addition, an inorganic encapsulation layer can effectively suppress oxygen and moisture permeation, but cracks or seams may occur in the inorganic encapsulation layer due to foreign matters or level differences (i.e. discontinuities caused by various step levels).
An organic layer planarizes the level difference (e.g., steps, tapers, or contact holes) made by a bank or a spacer and compensate foreign matters by covering cracks and seams at an inorganic encapsulation layer. However, despite such planarizing efforts, the organic layer cannot fully suppress oxygen and moisture permeation, and some amount of oxygen and moisture still permeate through the organic layer.